Biomechanical comparison of five cannulated screw fixation strategies for young vertical femoral neck fractures

• Published in: Journal of orthopaedic research Vol. 39; no. 8; pp. 1669 - 1680
• Main Authors: Jiang, Dajun, Zhan, Shi, Wang, Lei, Shi, Lewis L., Ling, Ming, Hu, Hai, Jia, Weitao
• Format: Journal Article
• Language: English
• Published: United States John Wiley and Sons Inc 01.08.2021
• Subjects: Biomechanical Phenomena; Bone Screws; cannulated screw fixation; Femoral Neck Fractures - diagnostic imaging; Femoral Neck Fractures - surgery; Finite Element Analysis; Fracture Fixation, Internal - methods; Humans; interfragmentary motion; patient‐specific finite element analysis; vertical femoral neck fractures; cannulated screw fixation; patient-specific finite element analysis; vertical femoral neck fractures; interfragmentary motion
• ISSN: 0736-0266; 1554-527X
• DOI: 10.1002/jor.24881

Vertical femoral neck fractures in patients younger than 65 years of age often require hip‐conserving surgeries. However, traditional fixation strategies using three parallel cannulated screws often fail in such patients due to an unfavorable biomechanical environment. This study compared different cannulated screw fixation techniques in patients via patient‐specific finite element analysis with linear tetrahedral (C3D4) elements. Forty vertical femoral neck fracture models were created based on computed tomography images obtained from eight healthy participants. Five different fixation strategies: alpha, buttress, rhomboid, inverted triangle, and triangle were assessed in walking status. Biomechanical parameters including stiffness, interfragmentary motion in two directions (detachment and shearing), compression force, and maximal implant stress were evaluated. The mean relative coefficient of strain distribution between the finite element analysis and experiment was from 0.78 to 0.94. Stiffness was highest (p < .05) in the buttress group (923.1 N/mm), while interfragmentary motion was lowest (p < .05) in the alpha group. Maximal stress was highest (p < .05) in the buttress group and lowest in the alpha group. Shearing values were significantly lower in the alpha group than in the rhomboid group (p = .004). Moreover, Shearing values were significantly higher (p = .027), while detachment values were significantly lower (p = .027), in the inverted triangle than in the triangle group. Clinical significance: Our results suggest that alpha fixation is the most reliable and biomechanically efficient strategy for young patients with vertical femoral neck fractures. Regular and inverted triangular fixation strategies may be suitable for fractures of different skeletal constructions due to antidetachment/shearing abilities.